> I can't recall the stratigraphical details, but _Protungulatum donnae_ is
> earliest Paleocene. The material comes from the Bug Creek Anthills of
> Montana.
Ah, the famous Bug Creek... I see. Thanks! :-) So this confirms that there
is no crown-group placental known from the Cretaceous.
> Some workers have followed Van Valen in regarding _Protungulatum_ as an
> arctocyonid, at least provisionally (e.g. Lillegraven, 1998). Another
> approach is to regard this genus as an ungulate (or ungulatomorph)
incertae
> sedis (e.g. McKenna and Bell, 1997; Archibald, 1998).
>
> In a recent study of the "condylarths", Muizon and Cifelli (2000) placed
> _Protungulatum_ close to the base of the Ungulatomorpha, but more derived
> than the zhelestids (the most primitive known ungulatomorphs).
Well, the zhelestids are now being put outside Placentalia, and the
geneticists say that Ungulata, -omorpha, -... are terribly polyphyletic
anyway...